A variety of fasteners can be used for anchoring structures in concrete or masonry. Self tapping anchors are generally formed of heat-hardened carbon steel.
Stainless steel provides good resistance to corrosion, but lacks the hardness required for self-tapping, heavy duty concrete fastener applications. Typically, such heavy duty fasteners require a very high hardness. A main challenge in using stainless steel for such applications involves the need to harden the tip of the fastener to a very high hardness in order to tap into the concrete.
Although 400 series stainless is capable of heat treatment and hardening, once heat treated, 400 series stainless loses a great deal of its corrosion resistant properties. In contrast, 300 series stainless has the corrosion resistance, however cannot effectively be heat treated to create the self tapping portion of the fastener.
One known solution is to create a bi-metal fastener, by welding or otherwise joining a carbon steel tip to the stainless body. This bi-metal part is then threaded and the carbon steel tip subsequently hardened. A bi metal solution is very expensive due to the number of manufacturing steps that are required.